weed eater won't stay running

It Starts, But Your Weed Trimmer Won’t Stay Running?

Here’s how you can fix it:

The title says it all, and stalling out is a pretty typical issue with your average string-based weed or hedge trimmers. We’ll go over some of the most common reasons why stalls such as these happen – and how to fix them – in this guide.

Why Is My Hedge or Weed Trimmer Motor Stalling?

Gasoline-powered weed trimmers typically work off a two-cycle engine, and need clean fuel, air, and a spark to start – The fuel and the spark start the ignition while the fuel and air combination keep the engine running. Trimmers that will start but sputter out at high speeds or when idling often have issues with air circulation, though there are a multitude of other causes to explore. Let’s start out with some of the easiest.

Store It Properly

Ounce of prevention, pound of cure – Make sure to take fuel out of your hedge trimmer if you’re planning on leaving it in storage for any significant length of time. Your fuel mix can go stale if left out for months at a time and make your trimmer hard to run, while both gas and oil will leave sticky, filter-clogging residues in the tank. A quick clean before storing for the winter can save a lot of effort come spring and summer.

Check Your Air Intake/Exhaust

When running the trimmer’s engine draws air into a combustion chamber via the intake port and then expels the air via the exhaust. Both the exhaust and the intake will need to be regularly cleaned and all air filters replaced on a regular basis – Both are typically easy to access, and replacement filters usually aren’t expensive.

In addition the exhaust port will have a “spark arrestor” located within, designed to catch and block any sparks from the engine – These can easily be cleaned with a wire brush or just replaced like your other filters.

Your Gas Tank Needs Air Too

Most weed eaters will have a small air hole available on the cap to the gas tank – This lets air into the tank to help prevent any vacuum from forming. An easy way to check if your air hole is clogged is to simply loosen the cap while the trimmer is running – If performance improves, a replacement gas cap is your fix.

When filling your gas reserve make sure not to fill it beyond the recommended line – Not only can this be a fire/explosion hazard this can also keep your fuel tank from delivering the proper amount of air into the fuel lines, leading to stalls.

Fuel Filters Can Be Clogged

Fuel filters are typically located inside the gas tank of a hedge trimmer – These are small, cylindrical filters attached to one or more hoses leading from the gas tank to the main body of the trimmer. Over time these will fill up with gunk and residue – More so if you have left your weed trimmer sitting up with fuel left inside.

Fuel filters for a weed eater are cheap and easy to replace at home with only a few minutes worth of work; check your manufacturer’s instruction booklet or website for details on the process or, failing that, a quick search on Youtube with your product model should net you what you need.

Make Sure You Have the Right Fuel Mix

If using a two-stroke engine that requires you to mix your own fuel double-check the recommended ratio and make sure your mix is right. Your trimmer should come with instructions on exactly what sort of mix you should be using (and make sure not to mix more than about a month’s supply at a time – Again, fuel can go “bad” and become ineffective if left to sit).

Checking the Choke

The choke supplies fuel to the engine to help it crank up from a cold start; if your choke is on the wrong setting this can lead to stalls. Before you crank the engine make sure your choke is in it’s full, highest position. While starting to crank move the choke down to the half-choke point and then make sure it is completely disengaged once the engine is fully started.

If your choke is left in a high position while the trimmer’s engine is running this will cause it to cut out. Make sure your choke is not sticky/wobbly or faulty in any way; a broken choke must be replaced if damaged.

Readjust Your Carburetor’s Settings

Sputtering and stalls can also be caused by an ill-adjusted carburetor. Look for two small screws on the side of the carburetor labeled “L” or “Lo” (Low) and “H” or “Hi” (High) (these may be flat-head or phillips). “L” adjusts the weed trimmer’s fuel usage while idling and “H” adjusts the fuel for the trimmer while running at its highest speed.

To adjust, crank your trimmer and, starting with the “L” screw, turn it slowly in the counterclockwise direction until the trimmer’s engine begins to slow down – Note the position of the screw head before turning the screw back in the clockwise direction until the engine begins to slow down again. Note this position as well.

When making the final adjustment you want the screw head to be as directly between these two positions as possible; unfortunately it isn’t an exact science but nailing down a “good enough” position should be fairly easy. Once done with the “L” screw head move on to the “H” screw and repeat the same process.

Side note: If you have a hard time keeping the engine running while working on the carburetor settings it might be a good idea to recruit a friend to help you out – One of you can keep the trimmer active while the other checks the carburetor adjustments.

Cleaning Your Carburetor

While we don’t recommend breaking down and servicing a carburetor at home a deep cleaning is never a terrible idea and should probably be done once per season before storage. To remove your carburetor first find and remove your drain float – This should be attached with a series of either two or four screws. Then remove the carburetor from your trimmer and spray thoroughly with carburetor cleaner, making sure to get in every divot, crack and crevice. Let this dry thoroughly before reattaching to your trimmer and then reattaching your float (note: be careful with your float, as an improper installation can lead to gas leaks).

If your carburetor is still not running smoothly after this cleaning it might need to be replaced or disassembled – While this can be done at home we thoroughly recommend taking it to a professional at this step unless you are absolutely certain you know what you’re getting into.

Upgrade to a Battery Powered Model

If the gas grime has got you down, why not go electric? Check out our guide to the best battery powered weed eaters that money can buy. It might save you some time!

The Final Word

Remember: If your weed trimmer starts but won’t keep running that’s usually a sign of either a poor fuel/air mix or an easy-to-replace filter having gotten clogged, all of which are easy fixes to perform at home. Next time your hedge trimmer gives you trouble we hope you remember our handy tips and can save some extra cash on repairs. Best of luck, and have fun trimming!

James Kennedy